464XLAT (https://tools.ietf.org/html/rfc6877), is a stateless NAT46 on the phone, coupled with a stateful NAT64 on the headend, and sometimes with DNS64.
This (edit: 'this' being the presence of stateless translation on the device) means the device has to do extra translation work on a per-packet basis, which would not help the battery life, and also the apps remains IPv4-only. I.e.: it is technical debt.
Apple has a stronger influence on the developers + a lot of address-family independent APIs, so they could exercise this option of allowing operation on IPv6-only access networks while also progressing towards all applications being future-proof.
This (edit: 'this' being the presence of stateless translation on the device) means the device has to do extra translation work on a per-packet basis, which would not help the battery life, and also the apps remains IPv4-only. I.e.: it is technical debt.
Apple has a stronger influence on the developers + a lot of address-family independent APIs, so they could exercise this option of allowing operation on IPv6-only access networks while also progressing towards all applications being future-proof.